The Soviet Union/Russia has not conducted any nuclear tests since 1990. Of the two major nuclear test sites owned by the Soviet Union, Semipalatinsk and Novaya Zemlya, the former was closed shortly before the collapse of the Soviet Union and subsequently left the jurisdiction of Russia due to the independence of Kazakhstan. 
In contrast, the Novaya Zemlya nuclear test site remains under the control of the 12th Main Directorate (12GUMO) of the Russian Ministry of Defence. As mentioned above, no nuclear explosive tests have been conducted there since 1990, but it has been used for subcritical tests to confirm the reliability of nuclear warheads, etc. In addition, the US government has indicated that some kind of nuclear-related experiment may be conducted in 2019, and the island of Novaya Zemlya is also home to the test site for the Burevestnik nuclear-powered cruise missile. 
In addition, from the summer of 2024, there have been observations of soil that may have been removed from the nuclear test tunnel.  In particular, satellite images taken in September showed a significant amount of soil being removed, and it is possible that extensive underground work is taking place inside the tunnel (it is also possible that this is related to the ground-level excavation work taking place in the surrounding area). 
At the same time, satellite images have confirmed the presence of large-scale construction on the island of Novaya Zemlya, the arrival of large transport ships and the arrival of Rosatom aircraft. 
At this stage, it would be inappropriate to jump to the conclusion that this is a sign that Russia will resume nuclear testing, etc. However, it is clear that large-scale activities are taking place on an unprecedented scale, and we need to keep a close eye on what their purpose is.